From: Jakub Jelinek <jakub@redhat.com>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>,
Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>,
linux-toolchains@vger.kernel.org,
Alistair Delva <adelva@google.com>,
Nick Clifton <nickc@redhat.com>
Subject: Re: [PATCH] Kbuild: implement support for DWARF5
Date: Wed, 4 Nov 2020 13:19:34 +0100 [thread overview]
Message-ID: <20201104121934.GT3788@tucnak> (raw)
In-Reply-To: <CAKwvOd=ez9nXCdQu6QRbNk5tfUAsSj9RLhopZtNE4RhDupg7+w@mail.gmail.com>
On Tue, Nov 03, 2020 at 02:21:22PM -0800, Nick Desaulniers wrote:
> > > This script fails for GCC 10.
> >
> > One thing is GCC DWARF-5 support, that is whether the compiler
> > will support -gdwarf-5 flag, and that support should be there from
> > GCC 7 onwards.
>
> I should improve my Kconfig check; I don't actually have a test for
> -gdwarf-5 for the compiler. In godbolt, it looks like -gdwarf-5
> produces an error from GCC up until GCC 5.1. Does (5.1 < GCC < 7) not
> produce DWARF5?
No. After all, those versions also predate DWARF5.
All 5.1 - 6.x did was start accepting -gdwarf-5 as experimental option
that enabled some small DWARF subset (initially only a few DW_LANG_* codes
newly added to DWARF5 drafts). Only GCC 7 (released after DWARF 5 has
been finalized) started emitting DWARF5 section headers and got most of the
DWARF5 changes in, e.g. including switching over most of the now
standardized GNU extensions from their DW_*_GNU_* codes to DWARF5 DW_*).
With GCC 5/6, you get:
echo 'int i;' | gcc -c -o /tmp/test.o -xc - -gdwarf-5; readelf -wi /tmp/test.o | grep Version:
Version: 4
while with 7+
Version: 5
instead.
> Maybe there's a more specific test you had in mind?
Guess what you want to test is what version you actually get in .debug_info
if you compile with -gdwarf-5.
> > Another separate thing is whether the assembler does support
> > the -gdwarf-5 option (i.e. if you can compile assembler files
> > with -Wa,-gdwarf-5) for GNU as I think that is binutils 35.1,
> > i.e. very new); but only if you want to pass the -Wa,-gdwarf-5
> > only when compiling *.s and *.S files. That option is about whether
> > the assembler will emit DWARF5 or DWARF2 .debug_line.
> > It is fine to compile C sources with -gdwarf-5 and use DWARF2
> > .debug_line for assembler files if as doesn't support it.
> >
> > Yet another thing is if you can pass -Wa,-gdwarf-5 even when
> > compiling C files. There are several bugs in that category that have been
> > fixed only in the last few days on binutils trunk, I'd suggest
> > just not to bother, GCC 11 will have proper test for fixed assembler
> > and will pass -gdwarf-5 to as when compiling even C sources with -gdwarf-5.
>
> Do you have links? I would prefer to do feature detection rather than
The
https://gcc.gnu.org/r11-3693
https://gcc.gnu.org/r11-4338
commits contain those tests in gcc/configure.ac
Jakub
next prev parent reply other threads:[~2020-11-04 12:20 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-22 1:21 [PATCH] Kbuild: implement support for DWARF5 Nick Desaulniers
2020-10-22 1:44 ` Fangrui Song
2020-11-03 22:27 ` Nick Desaulniers
2020-10-28 18:18 ` Nick Desaulniers
2020-11-02 2:20 ` Masahiro Yamada
2020-11-02 8:18 ` Jakub Jelinek
2020-11-03 22:21 ` Nick Desaulniers
2020-11-04 12:19 ` Jakub Jelinek [this message]
2020-11-03 22:13 ` Nick Desaulniers
2020-11-04 0:53 ` [PATCH v2 0/4] Kbuild: DWARF v5 support Nick Desaulniers
2020-11-04 0:53 ` [PATCH v2 1/4] x86_64: Change .weak to SYM_FUNC_START_WEAK for arch/x86/lib/mem*_64.S Nick Desaulniers
2020-11-04 0:53 ` [PATCH v2 2/4] Kbuild: do not emit debug info for assembly with LLVM_IAS=1 Nick Desaulniers
2020-11-05 6:58 ` Nathan Chancellor
2020-11-05 7:26 ` Fangrui Song
2020-11-09 18:28 ` Nick Desaulniers
2020-11-09 18:35 ` [PATCH v3] " Nick Desaulniers
2020-11-16 23:41 ` Nick Desaulniers
[not found] ` <CA+SOCLJTg6U+Ddop_5O-baVR42va3vGAvMQ62o9H6rd+10aKrw@mail.gmail.com>
2020-11-23 18:42 ` Nick Desaulniers
2020-11-24 18:44 ` Masahiro Yamada
2020-11-04 0:53 ` [PATCH v2 3/4] Kbuild: make DWARF version a choice Nick Desaulniers
2020-11-05 5:58 ` kernel test robot
2020-11-23 23:22 ` Arvind Sankar
2020-11-24 0:33 ` Segher Boessenkool
2020-11-24 16:56 ` Arvind Sankar
2020-11-24 17:46 ` Segher Boessenkool
2020-11-30 18:04 ` Masahiro Yamada
2020-11-30 20:27 ` Fāng-ruì Sòng
2020-12-01 3:38 ` Masahiro Yamada
2020-12-01 9:32 ` Segher Boessenkool
2020-12-02 1:08 ` Fāng-ruì Sòng
2020-11-30 20:45 ` Nick Desaulniers
2020-12-01 4:17 ` Masahiro Yamada
2020-11-04 0:53 ` [PATCH v2 4/4] Kbuild: implement support for DWARF v5 Nick Desaulniers
2020-11-24 17:28 ` Arvind Sankar
2020-12-03 23:22 ` Nick Desaulniers
2020-12-03 23:28 ` Nick Desaulniers
2020-12-04 17:06 ` Arvind Sankar
2020-12-10 23:18 ` Nick Desaulniers
2020-12-11 0:29 ` Arvind Sankar
2020-12-01 1:56 ` Masahiro Yamada
2020-11-04 0:00 ` [PATCH] Kbuild: implement support for DWARF5 Arvind Sankar
2020-11-04 0:05 ` Nick Desaulniers
2020-11-04 0:17 ` Arvind Sankar
2020-12-03 22:56 ` Nick Desaulniers
2020-12-04 0:17 ` Nick Desaulniers
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